In the manufacture of spring interiors such as are used to provide the inner spring assemblies of mattresses and similar products, spring assembler machines are employed to lace together rows of coil springs into arrays that are usually rectangular. Such arrays of springs are usually assembled as a plurality of vertically oriented helical coil springs often having hour-glass shapes, arranged horizontally in a grid that lies in a plane. The more preferred arrangements of spring interior manufacturing machines include a coil former, which makes individual springs from continuous wire, that feeds coil springs as they are formed to the assembly apparatus.
Efficient production of spring interiors is largely dependent on the speed with which springs can be fed to the assembler. Where the array of springs is made up of a plurality of identical springs evenly spaced in each of the rows, devices have been provided for automatically feeding rows of the springs to a transfer device and then translating the row with a multiple gripper mechanism bodily into the assembler, parallel to the previously transferred rows. One early version of such a machine is disclosed in U.S. Pat. No. 3,386,561 to Spuhl and a later version is disclosed in U.S. Pat. No. 3,774,652 to Strum. Such machines avoid the extra handling associated with loading the springs by coupling the output conveyor of a spring forming machine directly to the infeed of the transfer mechanism. As a rule, the speed of such a combination is limited by the spring coiling machine, which produces individual springs slower than the assembler can assemble them.
Attempts to speed up the spring interior assembly operation have led to the use of two coil forming machines instead of one, arranged with their output conveyors in parallel rows that extend through a transfer station. Such a combination is disclosed in U.S. Pat. No. 4,413,659 to Zangerle. In such a combination, the gripper mechanism at the transfer station operates to transfer rows of springs alternately from each of the output conveyors from the coilers, allowing one of the coilers to operate to produce one row of coils while the row of coils previously formed by the other coiler is being transferred to the assembler. With such an arrangement, each coiler may use the time required for two of the assembler machine cycles to produce one row of springs. Such an apparatus, however, still presents evenly spaced rows of coils to the transfer mechanism.
Many spring interior products are better formed when the coil springs are not uniformly spaced in the rows. However, combination machines of the type described above produce a steady stream or series of formed springs at the output of the toiler and present the coils to the transfer mechanism spaced evenly in rows. Where irregularly spaced coils are required, it has been necessary to feed the coils to the transfer mechanism evenly spaced to the average desired coil spacing and then to employ independently moveable grippers to transfer each of the springs to the assembler, moving different springs transversely in differing amounts in the transfer to achieve the desired irregular spring spacing. Assemblers with transfer mechanisms having such capability are illustrated and described U.S. Pat. Nos. 4,625,349 and 4,705,079 to Higgins, both hereby expressly incorporated by reference herein.
Even with the utilization of a spacing altering gripper mechanism at the transfer station, many spring interiors designs benefit from not only springs that are irregularly spaced, but include combinations of springs of more than one type, size or stiffness in each row. Direct connection of the output conveyors of spring coilers to the infeed of a transfer station does not alone provide such a capability. Accordingly, various manual steps are required in the handling of the springs fed to a spring interior assembler in order to produce many of the desired products. Further, in systems where speed of operation is desired, flexibility in the spacing and arrangement of springs is even more difficult to achieve.
The machines of the prior art do not provide the capacity, speed, flexibility of variable spring spacing or of mixing the types of springs that are presented on the conveyor to the transfer mechanism that feeds a spring interior assembly machine. Accordingly, there remains a need for faster and more flexible spring assembly methods and machines.